(a) Field of the Invention
The invention relates to a process for producing a packing material for use in liquid chromatography in which a specific epoxy-containing organic compound is used as the diluent.
(b) Description of the Invention
At present, liquid chromatography is a technique which is indispensable for the analisis, separation, etc. of nonvolatile substances. The market related to liquid chromatography is expanding rapidly. Accordingly, fierce competition in its technical development is being carried on by many companies. As one of the methods of regulating the separation ability of liquid chromatography, it is known to change the shape or amount of the pores in the filler. Among the methods of controlling the pores, the method exclusively used is to vary the molecular weight or cross-link density (amount of cross-linking agent) of the polymer. However, when the cross-link density is increased, the polymer particles become denser and the pore diameters smaller. This lowers the separation ability. Also, when the cross-link density is decreased, the mechanical strength of the polymer particles becomes lower. This constitutes a great obstacle to high-speed liquid chromatography.
Accordingly, a method was proposed as described in Japanese Patent Publication No. 31925/1982 which comprises aqueous suspension-polymerizing vinyl acetate with a cross-linking agent in the presence of an organic solvent as a diluent such as nitromethane or toluene which can be mixed with the monomer but is poorly miscible with water, saponifying the polymer and thereafter cross-linking the saponified polymer to produce a polyvinyl alcohol gel which is solid and porous.
However, by such a method in which an organic solvent is used as the diluent, it is necessary, in order to remove the diluent from the resulting polymer, to extract it with another organic solvent. If either of the solvents for dilution or extraction remains in the polymer, there will be a limitation to the field of application or an evil influence to the separation ability, so that there is a need for a complicated process for solvent removal and washing.
We conducted research into a process for producing a packing material for use in liquid chromatography which does not have the above-mentioned various defects. As a result, we have found that, by aqueous suspension polymerization in the presence of a specific epoxy group-containing compound as the diluent, it is possible to extract and remove the diluent from the resulting polymer easily with water without requiring any complicated process, and it is possible to produce a packing material for use in liquid chromatography which is uniform and porous and moreover is excellent in mechanical strength. The present invention is based on this discovery.
An object of the present invention is to provide a process for producing, in an industrially advantageous manner, a uniform and porous packing material for use in liquid chromatography which is excellent in mechanical strength.
Another object of the invention is to provide a process for producing a packing material for use in liquid chromatography which can be easily removed from the diluent with water, and which is not limited for the field of application and has no evil influences on the separation ability and work environment.
A further object of the invention is to provide an industrial process for producing a packing material for use in liquid chromatography, whose diameters of the pores in the resulting polymer can be easily regulated by suitably selecting the kind of specific epoxy group-containing compounds, and which therefore has various pore diameters applicable to many fields of use.
Other objects of the invention will become apparent from the following concrete explanation.